Conventionally, an inverter as one of power conversion devices is widely used. The inverter converts a direct current to an alternate current by controlling the conduction state of switching elements. The conduction state of a switching element (for example, an insulated gate bipolar transistor (IGBT)) is controlled by controlling a drive voltage to be applied between a gate and an emitter. A typical example of the inverter as described above is a three-phase inverter that converts a direct current to a three-phase alternate current by using six switching elements. The three-phase inverter is applied to, for example, an induction motor or a permanent magnet synchronous motor (hereinafter, “motor”). For example, such a motor as described above detects a motor current and executes control in accordance with the motor current. The motor uses a current-detecting shunt resistance for the current detection.
Patent Literature 1, for example, discloses a technique in which “a power-supply shunt resistance that detects a current between a DC power supply and an inverter device is provided, and between lower-arm switching elements and the negative side of the DC power supply, lower-arm shunt resistances for at least two phases are provided, each of which detects a phase current of the corresponding phase, such that a phase current which cannot be detected by the lower-arm shunt resistances is detected using the power-supply shunt resistance”.